Method of producing thermotropic liquid crystalline copolyester, thermotropic liquid crystalline copolyester composition obtained by the same method, and molding made of the same composition

ABSTRACT

A method of producing a thermotropic liquid crystalline copolyester having an extremely small amount of out-gases comprising the steps of: (1) charging in a reactor 5-100 mol % of aromatic hydroxycarboxylic acid, 0-47.5 mol % of aromatic dicarboxylic acid and 0-47.5 mol % of aromatic diol, so that the sum of mol % of each material is 100 mol % and the mol % of aromatic dicarboxylic acid and that of aromatic diol are substantially equal; (2) adding acetic anhydride of an amount which satisfies the formula, (B−C)/A≧1.04, “A” representing the total molar number of the hydroxy group in a reaction system, “B” representing the molar number of acetic anhydride to be added, and “C” representing the molar number of water present in the reaction system prior to addition of acetic anhydride; (3) acetylation; (4) melt polymerization; and (5) solid-phase polymerization.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method of producing athermotropic liquid crystalline copolyester which the amount ofcorrosive out-gases emitted in a high temperature environment isextremely small, a thermotropic liquid crystalline copolyester resincomposition obtained by the method, and a resin molded article made ofthe same resin composition for use in electrical/electronic components.More specifically, the present invention relates to a method ofproducing a thermotropic liquid crystalline copolyester which the amountof corrosive out-gases (such as acetic acid and phenol) emitted in ahigh temperature environment is extremely small due to the setting ofthe amount of acetic anhydride in the reaction system in whichacetylation is carried out before polymerization to a specific range, athermotropic liquid crystalline copolyester resin composition which theamount of corrosive out-gases (such as acetic acid and phenol) emittedin a high temperature is further extremely small and is made by mixing aspecific phosphite compound to a thermotropic liquid crystallinecopolyester resin obtained by the same method, and a resin moldedarticle made of the same resin composition for use inelectrical/electronic components.

[0003] 2. Description of the Related Art

[0004] It has been recognized that thermotropic liquid crystallinecopolyesters made by known methods tend to emit corrosive out-gaseswhich corrode metal-made conductive portions (e.g. an electroniccircuit) of an electric/electronic component in a high temperatureenvironment (such as soldering and mounting-to-surface processes).Corrosiveness of such corrosive out-gases has been recognized as aserious problem in such cases. Studies have revealed that the maincomponent of such corrosive out-gases is generally acetic acid (referto, for example, JP-A 8-53543).

[0005] Specifically, in electric/electronic components having metal-madeconductive portions which is vulnerable to the gases emitted from athermotropic liquid crystalline copolyester resin (such as a relay, aswitch, a connector, a socket, a resistor, a condenser, a motor, anoscillator, a print circuit board, and a power module), the metal-madeconductive portions are oxidized and a corrosive film is formed thereonby the corrosive out-gases and the like due to heat history during themounting-to-surfaces process. As a result, failure in the conductiveportions may occur. In addition, in a case in which theelectrical/electronic component has an electric contact which isoperated in a mechanical manner, a failure in contact may occur due toformation of layers of carbonized materials in the contact portion (thelayers are formed mainly in the contact portion by discharge during thecontact operation).

[0006] The corrosion of this type has particularly been a seriousproblem in components such as a relay and a switch in which good contactproperties must be maintained for a long period.

[0007] Recently, thermotropic liquid crystalline copolyesters are alsoused in various components in HDD (e.g. a carriage, a chassis and a VCMcoil holding member for an actuator, a member for installing a head in anon-operationphase and the like), in FDD and in similar components in anoptical disc drive and the like. With respect to the magnetic or opticaldata reading portions which are essential to these devices,deterioration of performances due to corrosive out-gases emitted fromthe resin are now likewise being concerned.

[0008] As thermotropic liquid crystalline copolyesters can be molded soas to have thin walls (i.e. these copolyesters have excellentmolding/fluxional properties) and have excellent soldering properties(i.e. these copolyesters have excellent heat resistance properties),they have been employed as forming materials of variouselectric/electronic components so that excellent dimensional precisionobtained in the copolyesters be most advantageously utilized. Inaddition, the electric/electronic components are now required to be farsmaller and operated at a lower voltage. Accordingly, formation ofcorrosive film and generation of layers of carbonized materials asdescribed above could cause much worse, more often initial failures ormalfunction in these electric/electronic components than now. Therefore,there is a demand for a thermotropic liquid crystalline copolyesterwhich the amount of corrosive gases is extremely small. This may beespecially a concern in a relay component and a switch component. Notethat the layers of carbonized materials are formed in these componentsprobably because the corrosive out-gases are carbonized by arc dischargeand deposited, causing abnormality in conductance.

[0009] As methods for reducing corrosive out-gases from themotropicliquid crystalline copolyester, there have been proposed a method ofblending a gas absorbing material (JP-A 8-333505), a method of blockingthe end of the molecular chain with mono-functional monomer (JP-A3-203925, JP-A 4-249528 and JP-A 8-53543). However, these methods arenot necessarily satisfactory.

[0010] These conventional methods propose, assuming that the maincomponent of the corrosive gases is acetic acid emitted from thethermotropic liquid crystalline copolyester, techniques for suppressingthe generation of acetic acid and capturing the generated acetic acid.However, it has not been determined what actually are the corrosiveout-gases which cause corrosive damages to metal-made conductiveportions of electric/electronic components. Therefore, although emissionof acetic acid is prevented, it does not necessarily mean that athermotropic liquid crystalline copolyester which is satisfactory interms of its corrosive out-gas effect on an electric/electroniccomponent can be obtained. Especially, if the technique pays too muchattention to suppression of acetic acid emission and rather increasesemission of other corrosive out-gases, such technique or methodsinevitably have to face a serious limitation.

[0011] With respect to this problem, the inventors have discovered thatthermotropic liquid crystalline copolyester may emit phenol, which iscorrosive and could be carbonized, together with acetic acid in a hightemperature environment. Based on this discovery, the inventors wereconvinced that a thermotropic liquid crystalline copolyester which theamount of corrosive out-gases is very small and thus can be used as areliable forming material for an electric/electronic component (in otherwords, a thermotropic liquid crystalline copolyester which satisfies thedemand from an electric/electronic component) is effected by suppressingthe generation of phenol. The present invention was completed as aresult of industrious study according to this theory.

[0012] The detailed mechanism in which corrosive out-gases are emittedfrom thermotropic liquid crystalline copolyester is not known yet. Theinventors, however, discovered for the first time in the world that theamount of emission of both corrosive out-gases (acetic acid and phenol)can be suppressed by setting the amount of acetic anhydride in thereaction system in which acetylation is carried out beforepolymerization within a specified range, resulting in the presentinvention.

[0013] Generation of corrosive gases tends to be accelerated by theexistence of inorganic or organic fillers blended into the copolyester.In the case of engineering plastics such as thermotropic liquidcrystalline copolyester, inorganic or organic fillers are normallyblended in practice. Accordingly, it is required that generation ofcorrosive gases be reliably suppressed in the resins in which inorganicor organic fillers are blended.

[0014] The inventors of the present invention have achieved reliablysuppressing generation of out-gases at a practically acceptable level inthe resin compositions in which fillers are blended, by adding aspecific phosphate compound into a thermotropic liquid crystallinecopolyester obtained by the aforementioned method.

OBJECTS OF THE INVENTION

[0015] One object of the present invention is to provide a method ofproducing a thermotropic liquid crystalline copolyester which the amountof corrosive out-gases (such as acetic acid and phenol) in a hightemperature environment is extremely small, a resin compositioncontaining a thermotropic liquid crystalline copolyester obtained by themethod, and electric/electronic components formed by molding the resincomposition. Another object of the present invention is to reliablysuppress generation of out-gases at a practically acceptable level inthe resin compositions in which fillers are blended.

SUMMARY OF THE INVENTION

[0016] As a result of assiduous study carried out by the inventors inorder to achieve the aforementioned objects, it has been discovered thatthe amount of emission of corrosive out-gases (both acetic acid andphenol) can be suppressed by setting the amount of acetic anhydride inthe reaction system in which acetylation is carried out prior topolymerization within a specific range. The present invention wascompleted on the basis of this discovery (method).

[0017] In addition, the inventors of the present invention havediscovered that a more excellent thermotropic liquid crystallinecopolysester which the amount of corrosive out-gases emitted in a hightemperature environment is extremely small can be obtained by blending aspecific phosphite compound into the thermotropic liquid crystallinecopolysester obtained by the method. This discovery also contributes tothe completion of the present invention.

[0018] Accordingly, in the first aspect of the present invention, amethod of producing a thermotropic liquid crystalline copolyester whichthe amount of out-gases is extremely small comprises the steps of: (1)feeding in a reactor 5-100 mol % of aromatic hydroxycarboxylic acid,0-47.5 mol % of aromatic dicarboxylic acid and 0-47.5 mol % of aromaticdiol, so that the sum of mol % of each material is 100 mol % and the mol% of aromatic dicarboxylic acid and that of aromatic diol aresubstantially equal; (2) adding acetic anhydride of an amount whichsatisfies the formula below,

(B−C)/A≧1.04

[0019] “A” represents the total molar number of the hydroxy group in areaction system, “B” represents the molar number of acetic anhydride tobe added, and “C” represents the molar number of water present in thereactions system prior to addition of acetic anhydride; (3) acetylation;(4) melt polymerization; and (5) solid-phase polymerization.

[0020] In the second aspect of the present invention, a thermotropicliquid crystalline copolyester resin composition comprises: (1) 100parts by weight of the thermotropic liquid crystalline copolyesterobtained by said method of producing a thermotropic liquid crystallinecopolyester; and (2) 0.001-1 parts by weight of at least one phosphiteester having the general formula:

[0021] In the formula, R and R′ each represent a group selected from thegroup consisting of alkyl group, alkenyl group, aryl group and aralkylgroup. R and R′ may represent the same group.

DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention will be described in detail hereinafter.

[0023] In a producing method of the present invention, as a first step(1), 5-100 mol % of aromatic hydroxycarboxylic acid, 0-47.5 mol % ofaromatic dicarboxylic acid and 0-47.5 mol % of aromatic diol are chargedin a reactor, so that the sum of mol % of each material is 100 mol % andthe mol % of aromatic dicarboxylic acid and that of aromatic diol aresubstantially equal. Types of the reactor and methods of charging thereaction materials are not particularly limited and any suitable knownmethods may be employed.

[0024] Monomers charged as the materials are, specifically, monomerswhich are derived to a repeating structural unit shown in formulae (2)to (4) below.

—O—(X)—CO—  (2)

—CO—(Y)—CO  (3)

—O—(Z)—O—  (4)

[0025] The monomer derived to the repeating unit of (2) is an aromatichydroxycarboxylic acid. Examples of the aromatic hydroxycarboxylic acidinclude p-hydroxybenzoic acid, 2-hydroxy-6-naphthoic acid,m-hydroxybenzoic acid and the like. These examples may be used solely orin combination. Preferably, p-hydroxybenzoic acid or a combination ofp-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid are used.

[0026] The monomer derived to the repeating unit of (3) is an aromaticdicarboxylic acid. Examples of the aromatic decarboxylic acid includeterephthalic acid, isophthalic acid, 2,6-dicarboxynaphthalene,4,4′-biphenyldicarboxylic acid and the like. These monomers may be usedsolely or in combination. Preferably, terephthalic acid or a combinationof terephthalic acid and isophthalic acid are used.

[0027] The monomer constituting the repeating unit of (4) is an aromaticdiol. Examples of the aromatic diol include 4,4′-biphenol, hydroquinone,2,6-dihydroxynaphthalene and the like. These monomers may be used solelyor in combination. Preferably, 4,4′-biphenol or a combination of4,4′-biphenol and hydroquinone are used.

[0028] In the thermotropic liquid crystalline copolyester produced bythe present invention, the preferable examples of monomer combinationinclude:

[0029] 1. p-hydroxybenzoic acid, terephthalic acid, p,p′-biphenol

[0030] 2. p-hydroxybenzoic acid, terephthalic acid and isophthalic acid,p,p′-biphenol

[0031] 3. p-hydroxybenzoic acid, terephalic acid and isophthalic acid,p,p′-biphenol and hydroquinone

[0032] 4. p-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid

[0033] 5. p-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid,terephalic acid and isophthalic acid, p,p′-biphenol

[0034] 6. p-hydroxybenzoic acid, terephthalic acid, isophthalic acid,2,6-dicarboxynaphthalene, p,p′-biphenol

[0035] The amount of the repeating structural unit (2) derived from thearomatic hydroxy acid such as p-hydroxybenzoic acid of the presentinvention is preferably set within the range of 5 to 100 mol % of thestructure unit as a whole of the copolyester produced by the method ofthe present invention. When the amount of the repeating structural unit(2) is less than 5 mol %, the melting point of the copolyester rises upand the fluxional properties and the mechanical strength thereofdeteriorate. This is not preferable.

[0036] Examples of more preferable combinations of the monomers include:aromatic hydroxycarboxylic acid containing 90-100 mol % ofp-hydroxybenzoic acid and 0-10 mol % of other aromatic hydroxycarboxylicacid (the sum of each mol % is 100 mol %); aromatic dicarboxylic acidcontaining 45-100 mol % of terephthalic acid and 0-55 mol % of otheraromatic dicarboxylic acid (the sum of each mol % is 100 mol %); andaromatic diol containing 60-100 mol % of p,p′-biphenol and 0-40 mol % ofother aromatic diol (the sum of each mol % is 100 mol %).

[0037] Examples of the most preferable combinations of the monomersinclude: aromatic hydroxycarboxylic acid containing 90-100 mol % ofp-hydroxybenzoic acid and 0-10 mol % of 2-hydroxy-6-naphthoic acid (thesum of each mol % is 100 mol %); aromatic dicarboxylic acid containing45-100 mol % of terephthalic acid and 0-55 mol % of isophthalic acid(the sum of each mol % is 100 mol %); and aromatic diol containing60-100 mol % of p,p′-biphenol and 0-40 mol % of hydroquinone (the sum ofeach mol % is 100 mol %).

[0038] By employing these preferable monomer combinations, the balancebetween the molding/fluxional properties, the heat resistance propertiesand the mold processing temperature is further improved, enabling moreexcellent adaptation and performances when the resulting resincomposition is molded to form an electric/electronic component havingthin walls. In addition to the aforementioned effect, the shear stresshistory during the molding process is reduced, the stability in a hightemperature environment and at the mold processing temperature isincreased and the basic properties of suppressing the emission ofcorrosive out-gases are improved, further enhancing the effect of thepresent invention.

[0039] With respect to the monomers and acetic anhydride (described indetail below), those which are industrially available may directly beused. The monomers may be dried before charging into the reactor or themonomers may be dried after being charged into the reactor. One exampleof a method of drying the monomers after the monomers are charged intothe reactor is follows. The temperature of the materials is raised to70° C. or so and then the “pressure reduction and nitrogen injection”process is repeated several times with stirring. By carrying out thisprocess for several hours, nitrogen-substitution and drying of themonomers are effected. Normally, drying in such a manner is sufficientin order to achieve the task. In a case in which the process is carriedout in a batch system, catalysts, stabilizer and the like may be chargedinto the reaction reactor according to necessity. As the catalysts,types thereof are not particularly limited and any suitable knowncatalysts may be used.

[0040] The reactions (including the acetylation step and the meltpolymerization step described below) may be carried out in a batchsystem or in a continuous system.

[0041] In the step (1), the monomers of predetermined type are chargedinto the reactor and heated according to necessity. Thereafter, as thestep (2), the amount of water contained in the reaction system ismeasured prior to charging of acetic anhydride.

[0042] Specifically, the factor to be first selected and controlledamong the variable factors associated with the reaction system in whichacetylation is carried out is the amount of acetic anhydride to becharged next. The amount of acetic anhydride to be charged next isexpressed by the following relationship, given that the total molarnumber of the hydroxy group of the monomers present in the reationsystem when the acetylation reaction is started is represented as “A”and the molar number of acedic anhydride is represented as “B” and themolar number of water present in the reaction system before the additionof acetic anhydride is represented by “C”.

(B−C)/A≧1.04

[0043] In the present invention, it is more preferable that “A”, “B” and“C” satisfy the following formula:

1.04≦(B−C)/A≦1.08

[0044] The value (B−C)/A is a parameter for determining the amount to beadded of acetic anhydride. When the value of the parameter is less than1.04, the amount of emission of phenol gas may increase and thus such avalue is not desirable. When the value of the parameter is larger than1.08, the amount of emission of acetic acid gas may significantlyincrease and thus such a value is not desirable, either. In short, aslong as the value of the parameter is no less than 1.04, it is possibleto suppress emission of phenol gas at a practically acceptable level,although a large amount of fillers has not been blended into the moldedbody.

[0045] In the present invention, in order to effect the aforementionedcontrol on the parameter, the amount of water present in the reactionsystem must be known and thus the water content in the reaction systemis measured prior to the starting of the acetylation process. As themethod of measuring the water content, any suitable known method may beemployed as long as the method allows reliable measurement of water of avery small amount (ppm or so). Specifically, Karl Fischer's method maybe employed as the method of measuring the amount of water.

[0046] In the present invention, the amount of water contained in thereaction system is measured prior to adding acetic anhydride. Even incase in which the monomers are dried before being charged (refer to thedescription above), a constant amount of water is still detected fromthe reaction system in a normal condition. The amount of water detectedin such a case is normally 0.2 weight % or so at the maximum.

[0047] One of the important features of the present invention lies inthat the amount of H₂O present in the reaction system is measured in thestep (2) and the amount of acetic anhydride to be consumed as a resultof the reaction between acetic anhydride and H₂O is calculated, in orderthat the amount of acetic anhydride be increased as much as thecalculated amount of acetic anhydride to be consumed. Because of this,in a case in which a batch system is employed, a portion of the chargedliquid is taken out as a sample from the reactor prior to the startingof the acetylation reaction and the amount of water contained therein ismeasured accurately. Note that any other suitable methods of measuringwater content may be employed.

[0048] Acetic anhydride added in step (2) is added in order to acetylatethe hydroxyl group of the monomers. Acetic anhydride easily reacts withH₂O and is decomposed to acetic acid. Accordingly, when water is presentin the reaction system, acetic anhydride immediately reacts with thiswater and is decomposed to acetic acid. As a result, the amount ofacetic anhydride which is substantially involved with the reaction inthe acetylation process is reduced. It should be noted that the amountof H₂O present in the reaction system significantly varies depending onthe method of producing the monomers, the conditions during storage,moisture in air, whether or not the monomers are dried in producingcopolyester, the degree of drying and the like. Therefore, the amount ofacetic anhydride to be added in producing thermotropic liquidcrystalline copolyester should be determined in consideration of theamount of H₂O contained in the monomers.

[0049] When acetic acid is generated as a result of the reaction betweenacetic anhydride and water, acetylation should be carried out by thisnewly produced acetic acid as well (at least theoretically). However,the actual rate of acetylation reaction of the hydroxyl group of themonomers caused by acetic acid is very slow, although the same reactioncaused by acetic anhydride proceeds quickly. Accordingly, when theremaining amount of acetic anhydride is scant, the rate of acetylationof the hydroxyl group of monomers during the acetylation process drops,making the rate of polymerization lower. In addition, the amount ofacetic anhydride not only affects the rate of polymerization, but alsoaffects as a key factor the emission amount of the out-gases (aceticacid and phenol, especially) from the obtained copolyester.

[0050] In short, the amount of acetic anhydride is calculated so thatthe effective amount of acetic anhydride satisfies the aforementionedconditions, a specific amount of acetic anhydride is charged in the step(2) based on the calculated value, and then the acetylation process iscarried out as the step (3).

[0051] The acetylation process is carried out with heating so that therefluxphase of acetic anhydride is maintained. The acetylation processis completed in 1-10 hours in a batch system, normally.

[0052] In the present invention, in addition to the aforementionedrelationship of the molar ratio, it is preferable that the acetylationprocess is carried out without discharging acetic acid out of thereaction system during the process and, after completing the acetylationprocess, the next melt polymerization reaction as the step (5)immediately follows without removing excess acetic anhydride and aceticacid generated by the acetylation process.

[0053] In other words, the acetylation process as described above iscarried out without discharging acetic acid in a reaction system inwhich adequately excessive acetic anhydride is present, and the processis immediately shifted to the polymerization reation. As a result, thefollowing effects that: (1) material balance in the system can bemaintained constant; (2) influence of water can be reliably eliminatedby carrying out removal of water contained in the system by aceticanhydride under heating; (3) the whole amount of the added aceticanhydride can be effectively utilized in the acetylation reaction; and(4) occurrence of excessive generation of oligomer can be suppressed,are probably obtained.

[0054] Although the relationship between these effects and thesuppression of emission of the corrosive out-gases (acetic acid andphenol) is not clear, it is assumed that, due to the improvement of theacetylation rate of the monomer groups before polymerization, thesuppression of generation of oligomers and the like, the polymerizationreaction afterwards uniformly proceeds. It is also assumed that, bysetting the value of (B−C)/A at 1.08 or less, the control of theside-reaction between acetic anhydride molecules and the reduction ofremaining acetic anhydride and remaining acetic acid are effected.

[0055] After completing the acetilation process, a copolyester can beproduced by the step (4) in which the temperature is raised so thatacetic acid is removed by distillation and, simultaneously with theremoval of the acetic acid, the melt polycondensation is carried out. Ina case in which p-hydroxybenzoic acid, terephthalic acid, isophthalicacid and 4,4′-biphenol are used as the materials, a copolyester can beproduced by distillating acetic acid within a temperature range of150-350° C. and performing, simultaneously with the removal of aceticacid, the melt polycondensation. The duration of polymerization can beselected within the range of 1 hour to dozens of hours.

[0056] In the melt polymerization step (5), the reaction base materialsthemselves act as reaction solvents. Accordingly, polymerization can beeffected without using reaction solvents in particular.

[0057] Suitable catalysts may be used in the acetylation process and/orthe polymerization process. The known catalysts for polycondensation ofconventional polyesters may be used. Examples of these catalystsinclude: metal salt catalysts such as magnesium acetate, tin (I)acetate, tetrabutyl titanate, lead acetate, sodium acetate, potassiumacetate, antimony trioxide and the like; and organic compound catalystssuch as N-methyl imidazol. The catalyst for the acetylation process maybe the same one as that for the polymerization process. Or, differentcatalysts may be used for each process. Normally, the catalysts arecharged with the monomers when the monomers are charged at the step (1)and used for the acetylation and the polymerization without beingremoved.

[0058] With respect to the polymerization reactor used for the meltpolymerization at the step (4), types thereof are not limited inparticular. However, the reactor is preferably a polymerization reactorof stirring reactor type having a stirring equipment used for highviscosity reaction in general. Such a stirring equipment includes astirring device of various configuration (anchor-shape,multi-step-shape, spiral-shape, spiral shaft-shape and the like) and astirring device as a modification of the aforementioned stirring device.More specifically, the polymerization reactor is preferably selectedfrom a Warner-type mixer, a Banbury mixer, a pony type mixer, Mullermixer, a roll mill, a kneader which can be continually operated, a pugmill, a gear compounder and the like. The reactor for the acetylationprocess and the polymerization reactor for the melt polymerization neednot be different and the same one reactor may be used for the twoprocesses.

[0059] The polymers obtained by the melt polymerization at the step (4)may further be subject to solid-phase polymerization. In the solid-phasepolymerization process, the polymer is first taken out of the meltpolymerization process at the step (4) and preferably milled to apowdery or flake-state. The polymer milled in such a manner is thensubject to solid-phase polymerization at the step (5) according to aknown solid-phase polymerization method. In a specific example of thesolid-phase polymerization method, the polymer is subject to a heattreating in a solid-phase for 1-30 hours within a temperature range of200-350° C. in an inert atmosphere such as nitrogen. The solid-phasepolymerization process may be carried out with stirring or the sameprocess may be carried out without stirring. The melt polymerization andthe solid polymerization may be carried out in the same one reactor, ifthe reactor is provided with a suitable stirring mechanism.

[0060] After the solid-phase polymerization, the obtained thermotropicliquid crystalline copolyester may be polletized in a known method, sothat the molding process can be effected using such a pellet.

[0061] The amount of out-gases such as acetic acid and phenol emittedfrom the thermotropic liquid crystalline copolyester obtained asdescribed above is very small. The specific emission limits applied tothe out-gases are different depending on the type of theelectric/electronic component. In the case of acetic acid, the emissionthereof is preferably 20 ppm or less and in the case of phenol, theemission thereof is preferably 5 ppm. When acetic acid and phenol ofamounts which exceed these limits (20ppm, 5ppm) are emitted, thepossibility that an electric/electronic component molded from thethermotropic liquid crystalline copolyester experiences operationalfailures becomes high, which is not desirable.

[0062] In addition, the thermotropic liquid crystalline copolyesterproduced as descirbed above exhibits further more excellent propertieswith respect to an emission-suppression effect of the corrosiveout-gases in a high temperature environment, by adding one or morephosphate esters as shown in the formula (1) below.

[0063] (In the formula, R and R′ each represent a group selected fromthe group consisting of alkyl group, alkenyl group, aryl group andaralkyl group. The number of carbon atoms of R or R′ is within the rangeof 1 to 50. R and R′ may represent the same group.)

[0064] Those having a pentaerythritol structure is preferred.

[0065] Specific examples of phosphate esters includebis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite,bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite, distearylpentaerythritol diphosphite, bis(dodecyl) pentaerythritol diphosphite.

[0066] Blending of the phosphite esters may be carried out either in theacetylation process or in the polymerization process. However, it ispreferable to blend the phophite esters into the polymers when thesolid-phase polymerization is completed. Addition of the phosphiteesters after the completion of the solid-phase polymerization ispreferable because the out-gas reduction effect by the addition of thephosphite esters is further enhanced in that case. The phosphite estersmay blended into the polymers according to a standard method. The timingof adding the phosphite esters may be selected from suitable timingsafter the aforementioned solid-phase polymerization. For example, thephosphite ester may be added with other fillers which will be describedbelow (or separately with these other fillers) when the thermotropicliquid crystalline polyester is pelletized after the solid-phasepolymerization.

[0067] The amount of the phosphite ester to be blended in the presentinvention is preferably within the range of 0.001-1 parts by weight withrespect to 100 parts by weight of the thermotropic liquid crystallinepolyester. In a case in which the amount of the phosphate ester blendedinto the polymer is less than 0.001 parts by weight, emission of phenolgas is not sufficiently reduced. On the other hand, in a case in whichthe amount of the phosphate ester blended into the polymer is more than1 part by weight, emission of gases resulting from the decomposition ofthe phosphite ester increases and causes an opposite effect, which isnot desirable. The amount of the phosphate ester blended into thepolymer is most preferably within the range of 0.01-0.5 parts by weightwith respect to 100 parts by weight of the thermotropic liquidcrystalline polyester.

[0068] The thermotropic liquid crystalline copolyester obtained from theproduction method of the present invention may be used for variouspurposes. Organic or inorganic fillers in a fiber, powder, particle orplatephase may generally be blended into the thermotropic liquidcrystalline copolyester in order to increase the mechanical strenagth ofthe copolyester.

[0069] Examples of the fillers in a fiber state include glass fiber,asbestos fiber, silica fiber, silica alumina fiber, potassium titanatefiber, carbon or graphite fiber, and fibrous materials made of metalsuch as aluminum, titanium, copper or the like. A representative examplethereof is glass fiber.

[0070] On the other hand, examples of the fillers in a particle stateinclude carbon black, graphite, silica, quartz powder, glass beads,milled glass fiber, glass balloon, glass powder, calcium silicate,aluminum silicate, talc, clay, silicates such as diatomaceous earth,wollastonite, or various metal containing powders such as iron oxides,titanium oxides, zinc oxides, antimony trioxide, alumina, calciumsulfate and others.

[0071] Examples of the fillers in a plate state include mica, glassflake, various metal foils and the like.

[0072] In addition, examples of the organic fillers include fibersthermalty stable high performance made of aromatic polyester, aromaticpolyimide and polyamide and the like.

[0073] These fillers may be treated with the conventional surfacetreatment agents prior to the use according to necessity. In a case ofusing fibrous fillers, a binder may be used as well.

[0074] In addition, an appropriate amount of various conventionaladditives such as antioxidant, heat stabilizer, weight-increasing agent,reinforcing agent, pigment, flame retardant agent and the like may beadded. These additives and fillers may be used as a combination of twoor more of additives and fillers.

[0075] When the fillers are used, the amount of the fillers blended intothe composition is to be within the range of 10 weight % to 90 weight %(preferably 80 weight %) of the composition overall. When the fillers isblended more than 90 weight % of the composition, the mechanicalstrength of the composition undesirably deteriorates. The fillers may beblended according to a known method. Whatever method is employed, thefillers are blended into the resin produced as a result of thesolid-phase polymerization. As described above, the phophite esters maybe added simultaneously with (or separately from) the adding of thefillers.

[0076] The thermotropic liquid crystalline copolyester resin compositionproduced by the method of the present invention as described above maybe subject to the conventional molding method including the standardmelt molding processing such as extrusion molding, injection molding,compression molding, blow molding and the like, such that the resin canbe processed to molded articles such as fibers, films, three-dimensionalmolded articles, containers, hoses and the like.

[0077] The molded articles obtained in such a manner may be subject to aheat treatment so that strength thereof be increased. Elasticity thereofcan often be increased at the same time by such a heat treatment. Theheat treatment may be carried out by heating the molded articles at atemperature no higher than the melting point of the polymer in an inertatmosphere (e.g. nitrogen, argon, helium or the like) or in anatmosphere containing oxygen (e.g. air) or in an environment in whichpressure has been reduced.

[0078] The thermotropic liquid crystalline copolyester of the presentinvention does not substantially emit or emits an extremely small amountof corrosive gases in a long-term use or in the use under ahigh-temperature environment (the soldering processing, themounting-to-surface processing, for example). Accordingly, when thethermotropic liquid crystalline copolyester is used as a formingmaterial of a member in which the corrosive out-gases emitted from theresin portion is problematic, various functions of the member can bereliably maintained without suffering from damages due to the corrosiveout-gases.

[0079] For example, when the thermotropic liquid crystalline copolyesterof the present invention is employed as a forming material of variouscomponents used in HDD (a carriage, a chassis, a VCM coil holdingportion of an actuator, a member for accommodating a head in annon-operation state), FDD and an optical disc drive, the amount of thecorrosive out-gases emitted from these components is significantlydecreased and thus the stability in the data-reading function isimproved.

[0080] Especially, when the thermotropic liquid crystalline copolyesteris employed in electric/electronic components having a metal-madeconductive portion which is vulnerable to the corrosive gases emittedfrom the resin (such as a relay, a connector, a socket, a resistor, acondenser, a motor, an oscillator, a printed circuit board, and a powermodule), the various functions of these components can be reliablymaintained without suffering from damages due to the corrosiveout-gases. Specifically, in an electric/electronic component made ofthermotropic liquid crystalline copolyester and having electric contactportions (such as a relay, a switch and the like), problems like aninitial failure caused by the formation of a corrosive film as a resultof oxidization of the contact portion by the corrosive out-gases and thelike and an contact failure caused by the formation of layers ofcarbonized materials at the application of voltage can be solved. Inother words, the functions of the component can be reliably maintained.Therefore, it is preferable that the resin portion of such anelectric/electronic component as described above is formed by thethermotropic liquid crystalline copolyester obtained by the method ofthe present invention.

[0081] When such the electric/electronic component as described above isproduced by using thermotropic liquid crystallineline copolyester, knownmolding methods including the insert molding method by injectionmolding, the encapsulating method or the like may be employed.

EXAMPLES

[0082] The present invention will be described far more in detail by thefollowing examples.

[0083] It should be noted that, as a result of the measurement accordingto a standard method, each thermotropic liquid crystalline copolyesterobtained by each of the following examples and comparative examplesshowed optically anisotropic properties when it was molten.

[0084] <Method of Measurement>

[0085] The property values shown in the examples were measured accordingto the following method.

[0086] (1) Melting Point

[0087] Measurement of the melting point was carried out, using α-aluminaas a reference material, by a DSC in which a differential scanningcalorimeter manufactured by Seiko Denshi Kogyo Co. was used. Thetemperature was raised from the room temperature to 420° C. at the rateof 20° C./minute so that the polymer was completely melted. Thetemperature was then dropped to 150° C. at the rate of 10° C./minute.The temperature was again raised to 430° C. at the rate of 20° C./minuteand the peak temperature observed in the heat absorption peak wasrecorded as the melting point.

[0088] (2) Apparent Viscosity

[0089] In measurement of the apparent viscosity, a capillary leometermanufactured by Intesco Co. (Model 2010) was employed. A capillary whosediameter was 1.0 mm, length was 40 mm and entrance angle was 900 wasused. Measurement was carried out at a shear rate of 100 sec⁻¹ from thetemperature which was 30° C. below the melting point measured by DSC, byheating so that the temperature was increased at a constant rate(specifically, at a temperature-increasing rate of +4° C./minute). Theapparent viscosity was obtained at a predetermined temperature.

[0090] (3) Water Content in the Monomer

[0091] Water content was measured at 175° C. by collecting about 2 g ofthe monomer and using a Karl Fischer's method water content measuringdevice (Model VA-05) manufactured by Mitsubishi Kasei Co.

[0092] (4) Amount of Out-Gases

[0093] The obtained thermotropic liquid crystalline copolyester wassubject to melt mixing and kneading by an extruder at a temperaturearound the melting point in order to produce pellets. The obtainedpellets were milled in the order of 1 mm or less. The resulting productwas heat-treated at 150° C. for 24 hours and the amounts of acetic acidand phenol gases generated after the heat treatment were each measuredby a gas chromatography.

[0094] Specific examples of measuring acetic acid and phenol gasesinclude a method in which the product produced by milling the pelletswas air-tightly sealed in a vial bottle of 20 ml, subject to a heatprocessing at 150° C. for 24 hours, and the amounts of the out-gases areeach obtained by analyzing the emitted gases by a gas chromatography.Examples of the method of injecting the gases in the vial bottle into agas chromatography device include a method in which injection ismanually carried out by a syringe and a method in which injection iscarried out by a head space sampler. In order to enhance the measurementprecision, it is preferable to use a head space sampler.

[0095] The type of the vial bottle, the aluminum cap, a septum and thelike used in this measurement are not particularly limited as long asthey are adaptable to a heat processing at 150° C. and any suitablemodels commercially available can be employed. In addition, the type ofthe column used for the gas chromatography analysis is not particularlylimited as long as it allows a quantitative analysis of acetic acid andphenol. However, a non-polar column is preferable. Examples ofpreferable columns include a glass column G-100 manufactured byKagakuhin Kensa Kyokai (Chemicals Testing Association). The conditionson temperature during measurement are not particularly limited as longas these conditions allow the separation of the peaks of acetic acid andphenol and the quantitative analysis thereof. Specific example of thesecondition include a condition in which the temperature is raised from45° C. to 280° C. at a temperature-increasing rate of 20° C./minute.

[0096] The measurement of the amount of the out-gases was actuallycarried out under the following conditions. (Pellets for measurement andthe method for measurement) The pellets were milled by a mill having 1mm φ mesh. The milled product was air-tightly sealed in a vial bottle of20 ml and subject to a heat treatment at 150° C. for 24 hours. Theamount of the acetic acid and phenol gases emitted as a result ofheating were quantitatively measured by a gas chromatography (HP6890)connected to a head space sampler (HP7694) manufactured by HewlettPackard Co. As the column, G-100 (40 m) manufactured by Kagakuhin KensaKyokai was employed. With respect to the other conditions, the initialtemperature was 45° C., the temperature-increasing rate was 20°C./minute, the final temperature was 280 C°, the pressure of helium was8.3 psi and the split ratio was 2.0. Measurement was carried out by aFID detection device.

[0097] (Molded Sample for Measurement)

[0098] The injection molding from the pellets was carried out by aninjection molding device manufactured by Niigata Tekkojo Co. (MIN-7) inthe conditions in which the molding temperature was 380° C., theinjection pressure 869 kg/cm², the injection rate 69.5 mm/sec, thedwelling pressure 790 kg/cm², the injection time 3 seconds, the coolingtime 12 seconds and the mold temperature 150° C. As a result, a testingpiece (20 mm×50 mm×1 mm thickness) for a tensile test was obtained.Using this testing sample, the amount of emission of the out-gases wasmeasured in a manner similar to that described above.

[0099] In a case in which the fillers such as milled glass fiber areblended into the composition, emission of the out-gases are more likelyto occur as compared with a case in which the fillers are not blended(this fact has been confirmed from the experiences in the past).Therefore, in the examples described below, the tests related to theout-gas emission were carried out using samples containing the fillers,in order that the comparison of the out-gas emission between theexamples be easier).

Example 1

[0100] A polymerization reactor made of SUS316 as a material and havinga double-helical stirring wing (manufactured by Nitto Koatsu Co.) wasused. Nitrogen-substitution was carried out by repeating the process of“pressure reduction of the polymerization reactor and nitrogen injectioninto the reactor” five times. Then, 1,330.10 g (9.63 moles) ofp-hydroxybezoic acid (HBA) manufactured by Ueno Seiyaku Co., 79.99 g(0.4815 moles) of isophthalic acid (IPA) manufactured by A.G.International Co., 453.29 g (2.7285 moles) of terephthalic acid (TPA)maufactured by Mitsui Sekiyu Kagaku Kogyo Co., 597.73 g (3.21 moles) ofp,p′-biphenol (BP) manufactured by Honshu Kagaku Kogyo Co. and 0.35 g ofmagnesium acetate as a catalyst manufactured by Tokyo Kasei Co. werecharged in the polymerization reactor and the monomers in thepolymerization reactor were mixed by stirring at the rotation rate ofthe stirring wing of 50 rpm. 2 g of the monomer mixture in thepolymerization reactor was taken out of the reactor and the watercontent therein was measured. 0.176 weight % of water content wasdetected in the monomer mixture. In other words, 4.33 g (0.24 moles) ofH₂O was present in the polymerization reactor.

[0101] The monomer which had been taken out of the reactor for themeasurement of water content therein was returned to the polymerizationreactor and 1,769.22 g (17.33 moles) of acetic anhydride manufactured byChisso Co. was added to the polymerization reactor. The temperature ofthe mixture was raised to 150° C. in 1 hour at the rotation rate of thestirring wing of 100 rpm and the acetylation reaction was carried outfor 2 hours with acetic anhydride being refluxed. After the acetylationreaction was completed, the temperature was raised at the rate of 0.5°C./minute in a state in which distillation of acetic anhydride wasallowed. The resulting polymers were taken out of the outlet provided atthe lower portion of the polymerization reactor at 330° C.

[0102] The polymers which had been taken out of the reactor were milledby a mill in the order of 1 mm or less and the solid-phasepolymerization was carried out by a solid-phase polymerization devicehaving a cylindrical rotational reactor manufactured by Asahi Garasu Co.Specifically, the polymers which had been milled as described above werecharged into the reactor, the nitrogen was circulated at a rate of 1litter/minute and the temperature was raised to 280° C. in 2 hours at arotation rate of 20 rpm. The temperature was kept at 280° C. for 1 hour,raised to 300° C. in 30 minutes and kept at the temperature for 4 hours.The product was then cooled to the room temperature in 1 hour, resultingin the aimed polymer.

[0103] The melting point of the obtained polymer was 376° C. whenmeasured by DSC. The apparent viscosity at the temperature of 410° C.was 1,110 poise.

[0104] 30 weight % of milled glass fiber (MJH20JMH-1-20) manufactured byAsahi Fiber Glass Co. was blended into 70 weight % of the obtainedthermotropic liquid crystalline copolyester. The mixture was compoundedby a twin-screw extruder of 30 mm φ (PCM-30) manufactured by IkegaiTekko Co. in which the maximum temperature of the cylinder was set at400° C. The composition in which 30 weight % of glass fiber was blended(pellet) was obtained. A testing piece for measurement of the out-gaseswas injection-molded from this pellet according to the aforementionedmolding method.

[0105] Similarly, 0.1 weight % of bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite as the phosphate ester (manufactured byAsahi Denka Kogyo Co., which will be referred to as “P-1” hereinafter)was blended into the mixture of the thermotropic liquid crystallinecopolyester and the milled glass fiber. Another pellet was thus obtainedand from this pellet, another testing piece for measurement of theout-gases was produced.

[0106] The effective amount of acetic anhydride is shown in Table 1. Themeasurement results of the out-gases from the pellet and the molding(the testing piece) made from the composition in which 30 weight % ofglass fiber was blended are shown in Table 2.

Example 2

[0107] A device which was similar to that used in Example 1 wasemployed. 1,330.10 g (9.63 moles) of p-hydroxybezoic acid (HBA), 79.99 g(0.4815 moles) of isophthalic acid (IPA), 453.29 g (2.7285 moles) ofterephthalic acid (TPA), 597.73 g (3.21 moles) of p,p′-biphenol (BP) and0.35 g of magnesium acetate as a catalyst were charged in thepolymerization reactor. The temperature in the polymerization reactorwas raised to 70° C. and the process of “pressure reduction ad nitrogeninjection” was repeated five times with rotating the stirring wing at 50rpm, effecting the nitrogen substitution and the drying of the monomersin 2 hours. After the drying of the monomers was completed, 2 g of themonomer mixture in the polymerization reactor was taken out of thereactor and the water content therein was measured. 0.015 weight % ofwater content was detected in the monomer mixture. In other words, 0.37g (0.02 moles) of H₂O was present in the polymerization reactor.

[0108] The monomer which had been taken out of the reactor for themeasurement of water content therein was returned to the polymerizationreactor and 1,739.61 g (17.04 moles) of acetic anhydride was added tothe polymerization reactor. The temperature of the mixture was raised to150° C. in 1 hour at the rotation rate of the stirring wing of 100 rpmand the acetylation reaction was carried out for 2 hours with aceticanhydride being refluxed. After the acetylation reaction was completed,the temperature was raised at the rate of 0.5° C./minute in a state inwhich distillation of acetic anhydride was allowed. The resultingpolymers were taken out of the outlet provided at the lower portion ofthe polymerization reactor at 330° C.

[0109] The polymers which had been taken out of the reactor were milledby a mill in the order of 1 mm or less and the solid-phasepolymerization was carried out by a solid-phase polymerization devicehaving a cylindrical rotational reactor. Specifically, the polymerswhich had been milled as described above were charged into the reactor,the nitrogen was circulated at a rate of 1 litter/minute and thetemperature was raised to 280° C. in 2 hours at a rotation rate of 20rpm. The temperature was kept at 280° C. for 1 hour, raised to 300° C.in 30 minutes and kept at the temperature for 4 hours. The product wasthen cooled to the room temperature in 1 hour, resulting in the aimedpolymer.

[0110] The melting point of the obtained polymer was 375° C. whenmeasured by DSC. The apparent viscosity at the temperature of 410° C.was 930 poise.

[0111] 30 weight % of the same milled glass fiber as used in Example 1was blended into 70 weight % of the obtained thermotropic liquidcrystalline copolyester. The mixture was compounded by a twin-screwextruder of 30 mm φ (PCM-30) in which the maximum temperature of thecylinder was set at 400° C. The composition in which 30 weight % ofglass fiber was blended (pellet) was obtained. A testing piece formeasurement of the out-gases was injection-molded from this pelletaccording to the aforementioned molding method.

[0112] Similarly, 0.1 weight % of the phosphite ester P-1 was blendedinto the mixture of the thermotropic liquid crystalline copolyester andthe milled glass fiber. Another pellet was thus obtained and from thispellet, another testing piece for measurement of the out-gases wasproduced.

[0113] The effective amount of acetic anhydride is shown in Table 1. Themeasurement results of the out-gases from the pellet and the moldedtesting piece made from the composition in which 30 weight % of glassfiber was blended are shown in Table 2.

Example 3

[0114] A device which was similar to that used in Example 1 wasemployed. Nitrogen substitution was carried out by repeating the processof “pressure reduction and nitrogen injection” of the polymerizationreactor five times. 1,330.10 g (9.63 moles) of p-hydroxybezoic acid(HBA), 132.90 g (0.80 moles) of isophthalic acid (IPA), 400.37 g (2.41moles) of terephthalic acid (TPA), 597.73 g (3.21 moles) ofp,p′-biphenol (BP) and 0.35 g of magnesium acetate as a catalyst werecharged in the polymerization reactor. The monomers in thepolymerization reactor were mixed by stirring at the rotating rate ofthe stirring wing of 50 rpm. 2 g of the monomer mixture in thepolymerization reactor was taken out of the reactor and the watercontent therein was measured. 0.200 weight % of water content wasdetected in the monomer mixture. In other words, 4.92 g (0.27 moles) ofH₂O was present in the polymerization reactor.

[0115] The monomer which had been taken out of the reactor for themeasurement of water content therein was returned to the polymerizationreactor and 1,785.55 g (17.49 moles) of acetic anhydride was added tothe polymerization reactor. The temperature of the mixture was raised to150° C. in 1 hour at the rotation rate of the stirring wing of 100 rpmand the acetylation reaction was carried out for 2 hours with aceticanhydride being refluxed. After the acetylation reaction was completed,the temperature was raised at the rate of 0.5° C./minute in a state inwhich distillation of acetic anhydride was allowed. The resultingpolymers were taken out of the outlet provided at the lower portion ofthe polymerization reactor at 330° C.

[0116] The polymers which had been taken out of the reactor were milledby a mill in the order of 1 mm or less and the solid-phasepolymerization was carried out by a solid-phase polymerization devicehaving a cylindrical rotational reactor. Specifically, the polymerswhich had been milled as described above were charged into the reactor,the nitrogen was circulated at a rate of 1 litter/minute and thetemperature was raised to 290° C. in 2 hours at a rotation rate of 20rpm. The temperature was kept at 290° C. for 6 hours and the product wascooled to the room temperature in 1 hour, resulting in the aimedpolymer.

[0117] The melting point of the obtained polymer was 356° C. whenmeasured by DSC. The apparent viscosity at the temperature of 370° C.was 980 poise.

[0118] 30 weight % of the same milled glass fiber as used in Example 1was blended into 70 weight % of the obtained thermotropic liquidcrystalline copolyester. The mixture was compounded by a twin-screwextruder of 30 mm φ (PCM-30) in which the maximum temperature of thecylinder was set at 370° C. The composition in which 30 weight % ofglass fiber was blended (pellet) was obtained. A testing piece formeasurement of the out-gases was injection-molded from this pelletaccording to the aforementioned molding method.

[0119] Similarly, 0.1 weight % of the phosphite ester P-1 was blendedinto the mixture of the thermotropic liquid crystalline copolyester andthe milled glass fiber. Another pellet was thus obtained and from thispellet, another testing piece for measurement of the out-gases wasproduced.

[0120] The effective amount of acetic anhydride is shown in Table 1. Themeasurement results of the out-gases from the pellet and the moldedtesting piece made from the composition in which 30 weight % of glassfiber was blended are shown in Table 2.

Example 4

[0121] A device which was similar to that used in Example 1 wasemployed. Nitrogen substitution was carried out by repeating the processof “pressure reduction and nitrogen injection” of the polymerizationreactor five times. 1,330.10 g (9.63 moles) of p-hydroxybezoic acid(HBA), 79.99 g (0.4815 moles) of isophthalic acid (IPA), 453.29 g(2.7285 moles) of terephthalic acid (TPA), 597.73 g (3.21 moles) ofp,p′-biphenol (BP) and 0.35 g of magnesium acetate as a catalyst werecharged in the polymerization reactor. The monomers in thepolymerization reactor were mixed by stirring at the rotating rate ofthe stirring wing of 50 rpm. 2 g of the monomer mixture in thepolymerization reactor was taken out of the reactor and the watercontent therein was measured. 0.180 weight % of water content wasdetected in the monomer mixture. In other words, 4.43 g (0.25 moles) ofH₂O was present in the polymerization reactor.

[0122] The monomer which had been taken out of the reactor for themeasurement of water content therein was returned to the polymerizationreactor and 1,703.88 g (16.69 moles) of acetic anhydride was added tothe polymerization reactor. The temperature of the mixture was raised to150° C. in 1 hour at the rotation rate of the stirring wing of 100 rpmand the acetylation reaction was carried out for 2 hours with aceticanhydride being refluxed. After the acetylation reaction was completed,the temperature was raised at the rate of 0.5° C./minute in a state inwhich distillation of acetic anhydride was allowed. The resultingpolymers were taken out of the outlet provided at the lower portion ofthe polymerization reactor at 330° C.

[0123] The polymers which had been taken out of the reactor were milledby a mill in the order of 1 mm or less and the solid-phasepolymerization was carried out by a solid-phase polymerization devicehaving a cylindrical rotational reactor. Specifically, the polymerswhich had been milled as described above were charged into the reactor,the nitrogen was circulated at a rate of 1 litter/minute and thetemperature was raised to 280° C. in 2 hours at a rotation rate of 20rpm. The temperature was kept at 280° C. for 1 hour, raised to 300° C.in 30 minutes and kept at the temperature for 6 hours. The product wasthen cooled to the room temperature in 2.5 hours, resulting in the aimedpolymer.

[0124] The melting point of the obtained polymer was 378° C. whenmeasured by DSC. The apparent viscosity at the temperature of 410° C.was 910 poise.

[0125] 30 weight % of the same milled glass fiber as used in Example 1was blended into 70 weight % of the obtained thermotropic liquidcrystalline copolyester. The mixture was compounded by a twin-screwextruder of 30 mm φ (PCM-30) in which the maximum temperature of thecylinder was set at 400° C. The composition in which 30 weight % ofglass fiber was blended (pellet) was obtained. A testing piece formeasurement of the out-gases was injection-molded from this pelletaccording to the aforementioned molding method.

[0126] Similarly, 0.1 weight % of the phosphite ester P-1 was blendedinto the mixture of the thermotropic liquid crystalline copolyester andthe milled glass fiber. Another pellet was thus obtained and from thispellet, another testing piece for measurement of the out-gases wasproduced.

[0127] The effective amount of acetic anhydride is shown in Table 1. Themeasurement results of the out-gases from the pellet and the moldedtesting piece made from the composition in which 30 weight % of glassfiber was blended are shown in Table 2.

Example 5

[0128] A device which was similar to that used in Example 1 wasemployed. Nitrogen substitution was carried out by repeating the processof “pressure reduction and nitrogen injection” of the polymerizationreactor five times. 1,330.10 g (9.63 moles) of p-hydroxybezoic acid(HBA), 79.99 g (0.4815 moles) of isophthalic acid (IPA), 453.29 g(2.7285 moles) of terephthalic acid (TPA), 597.73 g (3.21 moles) ofp,p′-biphenol (BP) and 0.35 g of magnesium acetate as a catalyst werecharged in the polymerization reactor. The monomers in thepolymerization reactor were mixed by stirring at the rotating rate ofthe stirring wing of 50 rpm. 2 g of the monomer mixture in thepolymerization reactor was taken out of the reactor and the watercontent therein was measured. 0.175 weight % of water content wasdetected in the monomer mixture. In other words, 4.31 g (0.24 moles) ofH₂O was present in the polymerization reactor.

[0129] The monomer which had been taken out of the reactor for themeasurement of water content therein was returned to the polymerizationreactor and 1,835.58 g (17.98 moles) of acetic anhydride was added tothe polymerization reactor. The temperature of the mixture was raised to150° C. in 1 hour at the rotation rate of the stirring wing of 100 rpmand the acetylation reaction was carried out for 2 hours with aceticanhydride being refluxed. After the acetylation reaction was completed,the temperature was raised at the rate of 0.5° C./minute in a state inwhich distillation of acetic anhydride was allowed. The resultingpolymers were taken out of the outlet provided at the lower portion ofthe polymerization reactor at 330° C.

[0130] The polymers which had been taken out of the reactor were milledby a mill in the order of 1 mm or less and the solid-phasepolymerization was carried out by a solid-phase polymerization devicehaving a cylindrical rotational reactor. Specifically, the polymerswhich had been milled as described above were charged into the reactor,the nitrogen was circulated at a rate of 1 litter/minute and thetemperature was raised to 280° C. in 2 hours at a rotation rate of 20rpm. The temperature was kept at 280° C. for 1 hour, raised to 300° C.in 30 minutes and kept at the temperature for 4 hours. The product wasthen cooled to the room temperature in 2.5 hours, resulting in the aimedpolymer.

[0131] The melting point of the obtained polymer was 376° C. whenmeasured by DSC. The apparent viscosity at the temperature of 410° C.was 1,250 poise.

[0132] 30 weight % of the same milled glass fiber as used in Example 1was blended into 70 weight % of the obtained thermotropic liquidcrystalline copolyester. The mixture was compounded by a twin-screwextruder of 30 mm φ (PCM-30) in which the maximum temperature of thecylinder was set at 400° C. The composition in which 30 weight % ofglass fiber was blended (pellet) was obtained. A testing piece formeasurement of the out-gases was injection-molded from this pelletaccording to the aforementioned molding method.

[0133] Similarly, 0.1 weight % of the phosphate ester P-1 was blendedinto the mixture of the thermotropic liquid crystallineline copolyesterand the milled glass fiber. Another pellet was thus obtained and fromthis pellet, another testing piece for measurement of the out-gases wasproduced.

[0134] The effective amount of acetic anhydride is shown in Table 1. Themeasurement results of the out-gases from the pellet and the moldedtesting piece made from the composition in which 30 weight % of glassfiber was blended are shown in Table 2.

Example 6

[0135] A device which was similar to that used in Example 1 wasemployed. 1,330.10 g (9.63 moles) of p-hydroxybezoic acid (HBA), 79.99 g(0.4815 moles) of isophthalic acid (IPA), 453.29 g (2.7285 moles) ofterephthalic acid (TPA), 597.73 g (3.21 moles) of p,p′-biphenol (BP) and0.35 g of magnesium acetate as a catalyst were charged in thepolymerization reactor. The temperature in the polymerization reactorwas raised to 70° C. and the process of “pressure reduction ad nitrogeninjection” was repeated five times with rotating the stirring wing at 50rpm, effecting the nitrogen substitution and the drying of the monomersin the polymerization reactor. After the drying of the monomers wascompleted, 2 g of the monomer mixture in the polymerization reactor wastaken out of the reactor and the water content therein was measured.0.013 weight % of water content was detected in the monomer mixture. Inother words, 0.32 g (0.02 moles) of H₂0 was present in thepolymerization reactor.

[0136] The monomer which had been taken out of the reactor for themeasurement of water content therein was returned to the polymerizationreactor and 1,671.21 g (16.37 moles) of acetic anhydride was added tothe polymerization reactor. The temperature of the mixture was raised to150° C. in 1 hour at the rotation rate of the stirring wing of 100 rpmand the acetylation reaction was carried out for 2 hours with aceticanhydride being refluxed. After the acetylation reaction was completed,the temperature was raised at the rate of 0.5° C./minute in a state inwhich distillation of acetic anhydride was allowed. The resultingpolymers were taken out of the outlet provided at the lower portion ofthe polymerization reactor at 330° C.

[0137] The polymers which had been taken out of the reactor were milledby a mill in the order of 1 mm or less and the solid-phasepolymerization was carried out by a solid-phase polymerization devicehaving a cylindrical rotational reactor. Specifically, the polymerswhich had been milled as described above were charged into the reactor,the nitrogen was circulated at a rate of 1 litter/minute and thetemperature was raised to 280° C. in 2 hours at a rotation rate of 20rpm. The temperature was kept at 280° C. for 1 hour, raised to 300° C.in 30 minutes and kept at the temperature for 6 hours. The product wasthen cooled to the room temperature in 2.5 hours, resulting in the aimedpolymer.

[0138] The melting point of the obtained polymer was 379° C. whenmeasured by DSC. The apparent viscosity at the temperature of 410° C.was 890 poise.

[0139] 30 weight t of the same milled glass fiber as used in Example 1was blended into 70 weight % of the obtained thermotropic liquidcrystalline copolyester. The mixture was compounded by a twin-screwextruder of 30 mm φ (PCM-30) in which the maximum temperature of thecylinder was set at 400° C. The composition in which 30 weight % ofglass fiber was blended (pellet) was obtained. A testing piece formeasurement of the out-gases was injection-molded from this pelletaccording to the aforementioned molding method.

[0140] Similarly, 0.1 weight % of the phosphite ester P-1 was blendedinto the mixture of the thermotropic liquid crystalline copolyester andthe milled glass fiber. Another pellet was thus obtained and from thispellet, another testing piece for measurement of the out-gases wasproduced.

[0141] The effective amount of acetic anhydride is shown in Table 1. Themeasurement results of the out-gases from the pellet and the molding(the testing piece) made from the composition in which 30 weight % ofglass fiber was blended are shown in Table 2.

Examples 7-10

[0142] 30 weight % of the same milled glass fiber as used in Example 1was likewise blended into the thermotropic liquid crystallinecopolyester obtained as a result of the solid-phase polymerization inExample 1. Further, in Example 7, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite (which will be referred to as “P-2”hereinafter) was added as 0.1 weight % of the phosphite ester. InExample 8, distearyl pentaerythritol diphosphite (which will be referredto as “P-3” hereinafter) was added as 0.1 weight % of the phosphateester. In Example 9, 2,2′-methylene bis(4,6-di-tert-butylphenyl)octylphosphite (which will be referred to as “P-4” hereinafter) wasadded as 0.1 weight % of the phosphate ester. In Example 10,tri(2,4-di-tert-butylphenyl) phosphate (which will be referred to as“P-5” hereinafter) was added as 0.1 weight % of the phosphate ester. Apellet was thus produced in each of Examples 7-10. A molding (testingpiece) was injection-molded from each pellet. It should be noted thatthe phosphate ester P-4 used in Example 9 and the phosphate ester P-5used in Example 10 are phosphate esters which are not represented by theaforementioned general formula (1).

[0143] The measurement results of the out-gases from the molding (thetesting piece) made from the composition in which 30 weight % of glassfiber was blended are shown in Table 2. TABLE 1 Effective Amount ofAcetic Anhydride in the Preparation of Thermotropic Liquid CrystallineCopolyester Effective Monomer OH Added Acetic H₂O in Acetic moleAnhydride Monomer Anhydride A mole B mole C (B − C)/A Example 1 16.0517.33 0.24 1.065 Example 2 16.05 17.04 0.02 1.060 Example 3 16.05 17.490.27 1.073 Example 4 16.05 16.69 0.25 1.024 Example 5 16.05 17.98 0.241.105 Example 6 16.05 16.37 0.02 1.019

[0144] TABLE 2 Measurement Results of Acetic Acid and PhenolGas-Emission Acetic Phenol Presence/Absence of Pellet or Acid GasExample No. Phosphite Additive Molded piece Gas (ppm) (ppm) Example 1Absent Pellet 8 2 Molded piece 7 7 P-1 added Pellet 8 2 0.1 wt % Moldedpiece 6 4 Example 2 Absent Pellet 3 2 Molded piece 2 9 P-1 added Pellet3 1 0.1 wt % Molded piece 3 3 Example 3 Absent Pellet 15 1 Molded piece13 6 P-1 added Pellet 14 1 0.1 wt % Molded piece 14 3 Example 4 AbsentPellet 0 35 Molded piece 0 49 P-1 added Pellet 0 23 0.1 wt % Moldedpiece 0 34 Example 5 Absent Pellet 89 1 Molded piece 82 6 P-1 addedPellet 88 1 0.1 Wt% Molded piece 86 3 Example 6 Absent Pellet 0 44Molded piece 0 52 P-1 added Pellet 0 29 0.1 wt % Molded piece 0 34Example 7 P-2 added Molded piece 8 2 0.1 wt % Example 8 P-3 added Moldedpiece 7 2 0.1 wt % Example 9 P-4 added Molded piece 8 8 0.1 wt% Example10 P-5 added Molded piece 6 7 0.1 wt %

[0145] As shown in Table 1, the effective amount of acetic anhydride iswithin the range of 1.04 to 1.08 in Example 1, Example 2 and Example 3.On the other hand, in Example 4 and Example 6, the effective amount ofacetic anhydride is less than 1.04. In Example 5, the effective amountof acetic anhydride is larger than 1.08. According to the measurementresults of the out-gas emission shown in Table 2, in a case in which theeffective amount of acetic anhydride is relatively small as in Example 4and Example 6, acetic anhydride was not detected but a relatively largeamount of phenol was detected. In a case in which the effective amountof acetic anhydride is relatively large as Example 5, a very smallamount of phenol gas was detected but a relatively large amount ofacetic gas was emitted.

[0146] As compared with Examples 4-6, Examples 1-3 whose effectiveamount of acetic anhydride was within the range of 1.04 to 1.08 showedexcellent results in which the amount of emission of acetic acid andphenol gases was very small.

[0147] From these results, it is clearly understood that thethermotropic liquid crystalline copolyester produced according to theproduction method of the present invention emits a very small amount ofacetic acid and phenol gases.

[0148] According to the present invention, in a method in which athermotropic liquid crystalline copolyester is produced by firstacetylating the hydroxyl group of monomers by acetic anhydride and thenperforming melt polymerization (or two-stage polymerization of meltpolymerization and solid-phase polymerization), it is possible toprovide a liquid crystalline copolyester which emits a very small amountof acetic acid and phenol gases by limiting the amount of aceticanhydride to a specific range.

[0149] Further, in the present invention, a phosphite ester having aspecific structure is blended into the thermotropic liquid crystallinecopolyester produced by first performing acetylation by a specificamount of excessive acetic anhydride and then melt polymerization ortwo-stage polymerization of melt polymerization and solid-phasepolymerization. As a result, it is possible to provide a thermotropicliquid crystalline copolyester resin composition which emits a verysmall amount of phenol gas.

[0150] The thermotropic liquid crystalline copolyester of the presentinvention emits a very small amount of the corrosive out-gases which maycorrode metal-made conductive portions (such as a circuit) of anelectric/electronic component, although the copolyester is used for along period or in a high temperature environment (e.g. the solderingprocess, the mounting-to-surface process). Accordingly, variousfunctions of the component in which said resin is used as a formingmaterial can be reliably maintained.

[0151] For example, when the thermotropic liquid crystalline copolyesterof the present invention is employed as a forming material of variouscomponents used in HDD (a carriage, a chassis, a VCM coil holdingportion of an actuator, a member for accommodating a head in annon-operation state), FDD and an optical disc drive, the amount of thecorrosive out-gases emitted from these components is decreased and thusthe stability in the data-reading function is improved.

[0152] Especially, when the thermotropic liquid crystalline copolyesteris employed in electric/electronic components having a metal-madeconductive portion which is structurally vulnerable to the corrosivegases emitted from the resin (such as a relay, a connector, a socket, aresistor, a condenser, a motor, an oscillator, a printed circuit board,and a power module), problems like an initial failure caused by theformation of a corrosive film as a result of oxidization of the contactportion by the corrosive out-gases and the like and an contact failurecaused by the formation of layers of carbonized materials at theapplication of voltage can be solved. Accordingly, the various functionsof these components can be reliably maintained. Specifically, in a relayand a switch having electric contact portions, solving theaforementioned problems means that the various functions of thesecomponents can be reliably maintained and thus the quality of thesecomponents is improved as a whole.

[0153] The emission of the corrosive gases tends to be accelerated byblending fillers into the resin. However, emission of the corrosivegases can be suppressed at a practically acceptable level by preferablyblending a specific phosphate ester into the resin, although the resinitself would easily emit the corrosive gases by blending of fillers.

What is claimed is:
 1. A method of producing a thermotropic liquidcrystalline copolyester which the amount of out-gases emitted therefromis very small comprising the steps of: (1) charging in a reactor 5-100mol % of aromatic hydroxycarboxylic acid, 0-47.5 mol % of aromaticdicarboxylic acid and 0-47.5 mol % of aromatic diol, so that the sum ofmol % of each material is 100 mol % and the mol % of aromaticdicarboxylic acid and that of aromatic diol are substantially equal; (2)adding acetic anhydride of an amount which satisfies the formula below,(B−C)/A≧1.04 “A” represents the total molar number of the hydroxy groupin a reaction system, “B” represents the molar number of aceticanhydride to be added, and “C” represents the molar number of waterpresent in the reaction system prior to addition of acetic anhydride;(3) acetylation; (4) melt polymerization; and (5) solid-phasepolymerization.
 2. A method of claim 1 , further comprising a step ofmeasuring water content in the reaction system between the step (1) andthe step (2).
 3. A method of claim 1 , wherein the value of (B−C)/A iswithin the range of 1.04 to 1.08.
 4. A method of claim 1 , wherein thearomatic hydroxycarboxylic acid contains 90-100 mol % ofp-hydroxybenzoic acid and 0-10 mol % of other aromatic hydroxycarboxylicacid, such that the sum of each mol % is 100 mol %, the aromaticdicarboxylic acid contains 45-100 mol % of terephthalic acid and 0-55mol % of other aromatic dicarboxylic acid, such that the sum of each mol% is 100 mol %, and the aromatic diol contains 60-100 mol % ofp,p′-biphenol and 0-40 mol % of other aromatic diol, such that the sumof each mol % is 100 mol %.
 5. A method of claim 1 , wherein thearomatic hydroxycarboxylic acid contains 90-100 mol % ofp-hydroxybenzoic acid and 0-10 mol % of 2-hydroxy-6-naphthoic acid, suchthat the sum of each mol % is 100 mol %, the aromatic dicarboxylic acidcontains 45-100 mol % of terephthalic acid and 0-55 mol % of isophthalicacid, such that the sum of each mol % is 100 mol %, the and aromaticdiol contains 60-100 mol % of p,p′-biphenol and 0-40 mol % ofhydroquinone, such that the sum of each mol % is 100 mol %.
 6. Athermotropic liquid crystalline copolyester resin compositioncomprising: (1) 100 parts by weight of the thermotropic liquidcrystalline copolyester obtained by the method of claim 1 ; and (2)0.001-1 parts by weight of at least one phosphite ester having thegeneral formula (1):

wherein R and R′ each represent a group selected from the groupconsisting of alkyl group, alkenyl group, aryl group and aralkyl group,and R and R′ may represent the same group.
 7. A thermotropic liquidcrystalline copolyester resin composition compring: (1) 100 parts byweight of the thermotropic liquid crystalline copolyester obtained bythe method of claim 1 ; (2) 0.001-1 parts by weight of at least onephosphorous acid ester having the general formula (1):

wherein R and R′ each represent a group selected from the groupconsisting of alkyl group, alkenyl group, aryl group and aralkyl group,and R and R′ may represent the same group; and (3) inorganic or organicfillers within the range of 10 to 90 weight % of the whole composition.8. An electric/electronic component comprising: a resin portion; and ametal-made conductive portion, wherein the resin portion is made of thethermotropic liquid crystalline copolyester obtained by the method ofclaim 1 .
 9. An electric/electronic component comprising: a resinportion; and a metal-made conductive portion, wherein the resin portionis made of the thermotropic liquid crystalline copolyester resincomposition of claim 6 or claim 7 .